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International Journal of Emerging Engineering Research and Technology
Volume 7, Issue 9, 2019, PP 7-18
ISSN 2349-4395 (Print) & ISSN 2349-4409 (Online)
International Journal of Emerging Engineering Research and Technology V7 ● I9 ● 2019 7
Optimization, Kinetics and Thermodynamics Study of
Transesterification of Neem Oil Using Heterogeneous Catalyst
Derived from Waste of Goat Bones
Wisdom ChukwuemekeUlakpa1*
, CallistusNonso Ude2, Ruth.O.Ulakpa
3
1Chukwuemeka Odumegwu Ojukwu University, Department of Chemical Engineering, P.M.B 02, Uli,
Anambra State, Nigeria 2Engineering Research Development and Production Department, Projects Development Institute
(PRODA), Enugu State, Nigeria 3Enugu State University of Science and Technology, Department Environmental Management, P.M.B.
01660, Enugu State., Nigeria
*Corresponding Author: Wisdom Chukwuemeke Ulakpa, Chukwuemeka Odumegwu Ojukwu
University, Department of Chemical Engineering, P.M.B 02, Uli, Anambra State, Nigeria, Email: [email protected]
INTRODUCTION
Fast depletion of world’s petroleum reserves
and increasing ecological concerns has created a
great demand for environmentally benign
renewable energy resources (Ashish et al.,
2010). There is an increasing worldwide concern
for environmental protection and for the
conservation of non-renewable natural resources.
For this reason the possibility of developing
alternative energy source to replace traditional
fossil fuels has been receiving a large interest in
the last few decades (Vicente et al., 1998).
Biodiesel is considered as a possible alternative
and future fuel for diesel engine due to the
predicted shortage of fossil fuels and increase in
the price of the petroleum.
It is biodegradable, renewable, non-toxic,
environmentally-friendly, and has high flash
point, better lubrication, high cetane number and has quite resemblance in regard with physical
and chemical characteristics with that of
conventional diesel fuel (Sanjay, 2013;
Demirba2003; Kaya et al., 2009; Hetsi et al., 2009). Biodiesel is the mixture of mono alkyl
esters that can be continuously derived from
vegetable oils or animal fats and therefore it is termed as renewable energy (Lin et al., 2006).
Several studies have shown that biodiesel is a
better fuel than fossil based diesel in terms of
engine performance, emissions reduction, lubricity, and environmental benefits (Canakci
et.al., 1997; Peterson et al.,1997).
Different types of catalysts such as base, acid or lipase are used in transesterification for
biodiesel synthesis but the base-catalyzed
reaction is the most common in the industry due to easier, faster and cheaper processing (Hassan
et al., 2013). The conventional catalysts used for
transesterification are homogeneous and
heterogeneous catalysts. The biodiesel industry is dominated by application of homogeneous
catalysts (such as KOH, NaOH and CH3ONa)
because of their easy usage and short time
ABSTRACT
In this study, calcium oxide (CaO) derived from waste bone (from goat) was used as catalyst for the
transesterification of neem seed oil (NSO). The catalyst was characterized using scanning electron
microscope (SEM).The transesterification was optimized using response surface methodology (RSM).
Under the optimal conditions of methanol to oil molar ratio of 8:1, catalyst concentration of 4.0wt %,
reaction temperature of 550C, reaction time of 4hr and agitation speed of 400rpm, 92.0% biodiesel was
achieved. The reaction kinetics conforms to a pseudo-second order rate law with reaction rate constants of
1.96E-5, 2.17E-5 and 5.18E-5, at 45, 50 and 550C, respectively. Activation energy (EA) for the reaction was 90.98 kJ/mol and pre-exponential factor of1.46E10dm3mol-1min-1.Thermodynamic parameters calculated for the
reaction show the enthalpy and entropy for the process to be 90.98 kJ mol-1 and 0.195 kJ mol-1 respectively.
The Gibbs free energy was calculated to be -28.63, 28.84 and 26.95 kJ mol-1 at 45, 50 and 55oC,
respectively.
Keywords: Transesterification, Kinetics, Catalyst, Optimization, Neemseed oil, Thermodynamics.
Optimization, Kinetics and Thermodynamics Study of Transesterification of Neem Oil Using Heterogeneous
Catalyst Derived from Waste of Goat Bones
8 International Journal of Emerging Engineering Research and Technology V7 ● I9 ● 2019
required for conversion of triglycerides to biodiesel (Demirbas 2008; Sharmaet al., 2011).
However, the use of homogeneous catalysts
requires neutralization and separation from the
final reaction products leading to a series of environmental concerns such as production of
waste water and corrosion problems (Georgogianni
et al., 2009).
Among heterogeneous catalysts which have
been researched, calcium oxide a solid base
catalyst shows high potential/promising result in
transesterification process with oil conversion of more than 95% (Liu et al., 2008). This catalyst
is low cost, low methanol solubility, non-corrosive,
environmental friendly and able to be reused for several times (Boey et al., 2011).There are
various processes/techniques that have been
adopted in production of biodiesel from vegetable oils and animal fats namely: dilution, micro-
emulsification, pyrolysis and transesterification
process/ technique (Demirbas et al., 2009;
Aderemi et al., 2010; Leng et al., 1999; Jabalu et al., 2009). Among these methods, transesterification
is the key and foremost important process to
produce the cleaner and environmentally safe fuel (Younis et al., 2009; Atlanatho et. al.,
2004). Biodiesel is produced through a chemical
process known as transesterification of different vegetable oil or animal fat with a short chain
alcohol, in which one mole of glyceride reacts
with three moles of alcohol in the presence of
appropriate amount of catalyst to form mono methyl ester and glycerol (Balat et al.,2010;
Demirbas 2009; Ghanei et al.,2011;Helwani et
al.,2009; Moradi et al.,2012).Transesterification of vegetable oils with low molecular weight
simple alcohols (methanol, ethanol, propanol,
butanol and amyl alcohol) has been established
as the best option to reduce the high viscosity, low volatility, heavy engine deposits and toxic
substance formation associated with the direct
use of vegetable oils (edible, non-edible, animal fats and used cooking oil) Schwab et.al.,(1987);
Tesser et.al., (2005).
The most common alcohols widely used are methyl alcohol and ethyl alcohol. Methanol,
found frequent application in the commercial
uses because of its low cost and its physical and
chemical advantages (Demirbas, 2005). Another advantage of using methanol is the separation of
glycerine, which can be obtained through simple
decantation (Nagi et. al., 2008).
The current feed stocks for production of
biodiesel or mono-alkyl ester are vegetable oil,
animal fats and micro algal oil. In the midst of them, vegetable oil is currently being used as a
sustainable commercial feedstock. There are
number of edible oil available in market i.e.
Sunflower oil, Soyabean oil, cotton seed oil, coconut oil, ground nut oil etc. from which
preparation of biodiesel can be achieved. But
use of edible oil is generally used for cooking purpose. Similarly if edible oil is used for
biodiesel production it can cause the shortage of
oil for cooking and the cost of oil may go high
(Hanumanth et al., 2012). However, it may cause some problems such as the competition
with the edible oil market, which increases both
the cost of edible oils and biodiesel. In order to overcome these disadvantages, many researchers
are interested in non-edible oils which are not
suitable for human consumption because of the presence of some toxic components in the oils
(Patni Neha et al., 2013).
The various non-edible oil which can be used
for the preparation of biodiesel are jatropha
oil(J. curcas), karanja oil(P. pinnata), Beef
tallow oil, used frying oil, other waste oil and
fats, Pongamia pinnate oil, Kokum oil, Mahua
oil (M. indica), Simarouba oil, willed apricot oil,
Jojoba oil, Tobacco seed oil (N. tabacum L.),
rice bran, mahua rubber plant (H. Brasiliensis),
castor oil, linseed oil, and microalgae, Kusum
oil, Neem oil (A. indica) and sal oil but the use
of these oils as a feed stock for production of
biodiesel varies as per their availability in
different parts of the world.
Different researchers synthesized and used
different kinds of solid wastes based catalysts (such as mollusk shells, eggshells, calcined fish
scale, sheep bone, calcined waste bone etc.) in
order to produce cost effective catalysts and
biodiesel (Viriya-Empikul et al., 2010; Jiang et al; 2015). Obadiah et al. (2012) worked on the
biodiesel production from palm oil using
calcined waste animal bone as catalyst. The biodiesel yield was 96.78 % under optimal
reaction conditions of 20 wt% of catalysts, 1:18
oil to methanol ratio, and 200 rpm of stirring of reactants and at a temperature of 65
0C.
Among these solid wastes, animal bone is one of
the best solid wastes that are easily and
abundantly available all over the world. Although, the waste bone derived catalysts have
shown a reasonable performance and constancy
in the reaction, however these catalysts are required in high amount, high methanol/oil
molar ratio with longer time for the reaction to
Optimization, Kinetics and Thermodynamics Study of Transesterification of Neem Oil Using Heterogeneous
Catalyst Derived from Waste of Goat Bones
International Journal of Emerging Engineering Research and Technology V7 ● I8 ● 2019 9
occur. All these disadvantages make waste bone derived catalysts practically and economically
unsuitable. To overcome these difficulties, it
would be imperative to impregnate waste animal
bones with other catalysts such as NaOH to make waste animal bone derived catalyst more
active and to boost the surface chemical properties.
Waste animal bones have proved to be highly effective as a catalyst support. The properties of
calcined bone make it advantageous for use as
catalyst support in transesterification reaction. It
contains hydroxyapatite [Ca10 (PO4)6(OH) 2], that is highly porous and also has a large surface
area which allows catalyst to disperse over it
largely and effectively. Calcined bones can also be used in high pressure and temperature reaction
conditions. The main influential parameters of
transesterification of vegetable oils are as follows: molar ratio of alcohol to oil, catalyst amount,
reaction temperature, mixing intensity, and reaction
time has been widely studied and optimized.
In this study, goat waste bone activated by
chemical means (alkaline) were used as catalyst
for the transesterification of neem seed oil
(NSO). The transesterification was optimized with
response surface methodology (RSM) using
central composite design (CCD). The use of
RSM addresses optimization by providing an
understanding of how the test variables affect
the selected process response, determining the
interrelationships between the test variables, and
characterizes the combined effect that all the
influential test variables may have on process
response. The kinetics of the reaction were studied
at the optimal conditions and the thermodynamic
properties were also evaluated.
MATERIALS AND METHODS
The non-edible neem seed oil was purchased
from National Research Institute for Chemical
Technology (NARICT) Zaria, Kaduna state,
Nigeria and the waste bones was sourced from a
local market (Kubwa village market), Kubwa,
Abuja. The physico-chemical properties of the
Neemseed oil are shown in Table 1. The chemicals
used include methanol, potassium hydroxide
and benzene. They were all of analytical grade.
The equipment used include Petri dish, various
sizes of beaker, different sizes of measuring
cylinders, thermometer, pipette hot plate with
magnetic stirrer arrangement used as a heating
and stirring device, separating funnel, digital
weighing balance, stop watch, laboratory oven,
filter paper, cotton wool, masking tape, conical
flasks.
Catalyst Preparation/Activation
The catalyst (waste animal bones) from goats
was sourced from a local market in Kubwa,
Abuja. The sourced waste bones was soaked in
boiling water for several hours (6-8 hours) at about 75
0C to remove tissues and fats in the
bone and then rinsed with distilled water for 3-4
times to remove dust and impurities. The waste bones were dried in the drying oven at 110
0C for
4hours to remove water and moisture before
being ground finely to a <2mm particle size
powder using a hammer mill. The crushed and powdered catalysts was sieved using various
mesh sizes (100-200) to get particle of uniform
size of mesh screens. They were stored in a desiccator in the presence of silica and KOH
pellets in order to avoid water and CO2 (reaction
with air)contact with the catalysts prior to further usage because the CaO catalyst will be
reacted with CO2 and converted intoCaCO3, thus
reducing its activity as a catalyst.
Catalyst Activation
Sample of the crushed/powdered waste bone
was impregnated with concentration of NaOH at
different mass solution on weight basis by dissolving the sodium hydroxide with deionized
water in the ratio of 2:1. The crushed/powdered
waste bone was impregnated with the prepared NaOH at different ratios of 1:2 to 1:6 (w/v) by
stirring vigorously. After the completion of the
impregnation process, it was dried at a
temperature of 110OC for 24hours then cooled
to room temperature and was washed with
distilled water and dried for 4 hours in an oven
at 120oC.
Characterization of Catalyst
Scanning Electron Microscope
The surface morphology of the prepared catalyst
from waste bone was observed under a scanning electron microscope (SEM) using a Phenom
Prox working at an accelerated voltage of
15kV.Micrographs were observed at 80𝜇𝑚and
100 𝜇𝑚 at magnification of 100x and 500x,
respectively.
Transesterification Reaction Procedures
The transesterification reaction was carried out in a three necked 250 ml round bottom flask
fitted with a thermometer, condenser and a
mechanical stirrer whose speed was also controlled The neemseed oil reacts with
methanol in the presence of catalyst derived
from waste of animal bone to produce methyl
Optimization, Kinetics and Thermodynamics Study of Transesterification of Neem Oil Using Heterogeneous
Catalyst Derived from Waste of Goat Bones
10 International Journal of Emerging Engineering Research and Technology V7 ● I9 ● 2019
esters of fatty acids (biodiesel) and glycerol. The refined neemseed oil (30ml) was quantitatively
transferred into a flat bottom flask placed on a
hot magnetic stirrer.
Then specific amount of catalyst (by weight of refined neemseed oil) dissolved in the required
amount of methanol was added. The reaction
flask was kept on a hot magnetic stirrer under constant temperature with defined agitation
throughout the reaction. At defined time 1-2 hours,
sample was taken out, cooled, and the biodiesel
(i.e. the methyl ester in the upper layer) was separated from the by-product (i.e. the glycerol
in the lower layer) by settlement overnight
under ambient condition. The percentage of the biodiesel yield was determined by comparing
the weight of layer biodiesel with the weight of
refined neemseed oil used.
The percentage conversion of each sample was
calculated from the below equation (Yusuf and
Sirajo, 2009).
Yield (%) = weight of methylester
weight of oil used x 100 (1)
Design of experiments
The experimental design for optimization was
done by applying response surface methodology
(RSM) with central composite design (CCD) to
investigate the influence process conditions. Design Expert software (version 10.0.6.0) was
used in this study to design the experiment and
to optimize the reaction conditions. The 2-level -5- factor fractional factorial experimental
design was employed in this study requiring 32
experiments consisting of 16 factorial points, 10
axial points and 6 center points. The level of each was chosen based on the importance to the
experiment.
The following five parameters (catalyst concentration (A),methanol to oil molar ratio
(B), and reaction temperature (C) reaction time
(D) and agitation speed (E) were varied in order to maximize the biodiesel yield. The experimental
range and level of independent variables of the
central composite design for the optimization of
the transesterification process are shown in Table 2
Table2. Experimental range and levels of the independent variables
Independent variable Units Low level (-1) High level (+1) -⍺ +⍺ 0 level
Catalyst conc. (A) Wt% 3(-1) 5(+1) 2(-2) 6(+2) 4
Methanol, (B) Mol/mol 6(-1) 10(+1) 4(-2) 12(+2) 8
Temperature, (C) °C 45(-1) 65(+1) 35(-2) 75(+2) 55
Reaction time (D) Hours 3(-1) 5(+1) 2(-2) 6(+2) 4
Agitation speed (E) Rpm 300(-1) 500(+1) 200(-2) 600(+2) 400
A quadratic polynomial equation by central
composite design was developed to predict the response as a function of independent variables
and their interaction (Razali et al., 2010). A
mathematical model, following a second –order
polynomial which includes interaction terms
was used to calculate the predicted response (Yasin, 2012).The response for the quadratic
polynomials is described below (Montgomery
2001):
Y= 𝛽0 + 𝛽𝑖𝑋𝑖𝑘𝑖=1 + 𝛽𝑖𝑖𝑋
2𝑖
𝑘𝑖=1 + 𝛽𝑖𝑗𝑋𝑖𝑋𝑗
𝑘𝑗=𝑖+1
𝑘𝑖=1 (2)
Where Y is % methyl ester yield, xi and xj are
the independent study factors(coded variables),
and 𝛽0 ,𝛽𝑖 ,𝛽𝑖𝑖 and 𝛽𝑖𝑗 are constant co-efficient,
regression co-efficient of the linear terms,
regression co-efficient of the quadratic terms,
and regression co-efficient of the interaction
terms, respectively, and k is the number of
factors studied and optimized in the experiment
(number of independent variables). The Design– Expert 10.0.6.0 software package was used for
regression analysis and analysis of variance
(ANOVA).
Table3. Experimental design matrix for 2-level 5 factors response design and the experimental values and
predicted values for biodiesel production from neem seed oil
Run
order
Catalyst conc.
(wt %)
A
Methanol/Oil
molar
ratio(mol)B
Temperature
(oC)
C
Time
(Hours)
D
Agitation Speed
(Rpm)
E
Expt.Yield
(%)
Pred.
Yield
(%) Coded Real Coded Real Coded Real Coded Real Coded Real
1 -1 3.0 -1 6:1 -1 45.0 -1 3.0 +1 500.0 43.00 41.88
2 +1 5.0 -1 6:1 -1 45.0 -1 3.0 -1 300 63.00 57.88
3 -1 3.0 +1 10:1 -1 45.0 -1 3.0 -1 300 70.00 62.88
Optimization, Kinetics and Thermodynamics Study of Transesterification of Neem Oil Using Heterogeneous
Catalyst Derived from Waste of Goat Bones
International Journal of Emerging Engineering Research and Technology V7 ● I8 ● 2019 11
4 +1 5.0 +1 10:1 -1 45.0 -1 3.0 +1 500 80.00 72.79
5 -1 3.0 -1 6:1 +1 65.0 -1 3.0 -1 300 60.00 56.88
6 +1 5.0 -1 6:1 +1 65.0 -1 3.0 +1 500 53.00 49.79
7 -1 3.0 +1 10:1 +1 65.0 -1 3.0 +1 500 53.00 47.79
8 +1 5.0 +1 10:1 +1 65.0 -1 3.0 -1 300 70.00 60.79
9 -1 3.0 -1 6:1 -1 45.0 +1 5.0 -1 300 60.00 61.88
10 +1 5.0 -1 6:1 -1 45.0 +1 5.0 +1 500 60.00 61.79
11 -1 3.0 +1 10:1 -1 45.0 +1 5.0 +1 500 33.00 33.79
12 +1 5.0 +1 10:1 -1 45.0 +1 5.0 -1 300 27.00 23.79
13 -1 3.0 -1 6:1 +1 65.0 +1 5.0 +1 500 33.00 36.79
14 +1 5.0 -1 6:1 +1 65.0 +1 5.0 -1 300 50.00 49.79
15 -1 3.0 +1 10:1 +1 65.0 +1 5.0 -1 300 77.00 74.79
16 +1 5.0 +1 10:1 +1 65.0 +1 5.0 +1 500 63.00 60.71
17 -2 2.0 0 8:1 0 55.0 0 4.0 0 400 60.00 61.29
18 -1 6.0 0 8:1 0 55.0 0 4.0 0 400 57.00 66.46
19 0 4.0 0 4:1 0 55.0 0 4.0 0 400 53.00 50.29
20 0 4.0 +2 12:1 0 55.0 0 4.0 0 400 43.00 55.46
21 0 4.0 0 8:1 -2 35.0 0 4.0 0 400 53.00 57.29
22 0 4.0 0 8:1 +2 75.0 0 4.0 0 400 57.00 62.46
23 0 4.0 0 8:1 0 55.0 -2 2.0 0 400 63.00 79.29
24 0 4.0 0 8:1 0 55.0 +2 6.0 0 400 73.00 67.46
25 0 4.0 0 8:1 0 55.0 0 4.0 -2 200 50.00 59.29
26 0 4.0 0 8:1 0 55.0 0 4.0 +2 600 47.00 48.46
27 0 4.0 0 8:1 0 55.0 0 4.0 0 400 82.00 90.38
28 0 4.0 0 8:1 0 55.0 0 4.0 0 400 85.00 90.38
29 0 4.0 0 8:1 0 55.0 0 4.0 0 400 93.00 90.38
30 0 4.0 0 8:1 0 55.0 0 4.0 0 400 92.00 90.38
31 0 4.0 0 8:1 0 55.0 0 4.0 0 400 92.00 90.38
32 0 4.0 0 8:1 0 55.0 0 4.0 0 400 91.00 90.38
The fitness of the model and the statistical
significance was evaluated using analysis of
variance (ANOVA). ANOVA was also used to
determine the significance of the individual
terms, interacting terms and also the quadratic
terms.
RESULTS AND DISCUSSIONS
Characterization of the catalyst
Scanning Electron Microscope Analysis
The SEM images of the activated catalyst at
different magnifications are shown in Fig.1.The
morphology of the alkaline activated waste bone
at magnifications of 1000xhas smooth surface
with little cavities which result from evaporation
of the activating agent (NaOH).The surface
morphology with magnifications of 500x has
smooth surface with no cavities and hair line
cracks. This could be as a result of the activation
process which might have filled up the holes
thereby giving it a smooth surface.
Figure1. SEM images of alkaline waste bone at
different magnifications
Optimization, Kinetics and Thermodynamics Study of Transesterification of Neem Oil Using Heterogeneous
Catalyst Derived from Waste of Goat Bones
12 International Journal of Emerging Engineering Research and Technology V7 ● I9 ● 2019
Modelling and optimization of the transesterification reaction
Development of regression model
The regression equation as a function of the selected variables for FAME yield (%) is given by:
Yield=+90.38+1.29*A+1.29*B+1.29*C-2.96*
D-2.71*E-1.44*AB-0.69*AC-2.69*AD+9.31*AE+5.06*BC-3.44*BD+1.81*BE+3.81*CD
3.19*CE+0.56*DE-6.62∗ A2-9.38∗ B2-7.63∗ C2-4.25∗ D2-9.18*E2 . (3)
where “Y” is the response, that is the conversion
to biodiesel, and A, B, C,D and E shows the
values of the test variables, catalyst concentration,
methanol to oil molar ratio, temperature,
reaction time and agitation speed respectively.
The Positive sign in front of the terms indicates
synergistic effect in increase FAME yield.while
negative sign indicates antagonistic effect of the factor (Shuit et al. 2010). The model regression
equation(equation 3) indicated that the positive
coefficients indicated linear to increase the FAME yield.Although,the quadractic termshad
negative effects that decrease the FAME
yield. Hence, the model reduces to equation
4 after eliminating the insignificant coefficients.
Y=+90.38+1.29*A+1.29*B+1.29*C+9.31*AE+5.06*BC+1.81*BE+3.81*CD+0.56*DE (4)
The result of statistical analysis of variance
(ANOVA) which was carried out to
determine the significance and fitness of the
quadratic model as well as the effect of significant individual terms and their interaction
on the FAME is presented in Table 4.The Model
F-value of 168.19 and Prob>F of < 0.0001 implied that the model is significant at 95%
confidence level.The Prob>F or p-value
(probability of error value) is a tool used to
determine the significance of each regression coefficient as well as interaction effect of each
cross product.
The smaller the p-value, the bigger the
significance of the corresponding coefficient is
(Chen et al. 2008).In this case, the p-values less
than 0.05 indicated that the particular term is
statistically significant.The value of regression
coefficient R2 for the model is 0.9967,
indicating the good fitness of the model. High
values of predicted R2 (0.9906) and adjusted
coefficient of determination (R2 Adj:0.9908)
and low value of coefficient of variation
(C.V) (2.71%), are an indication of precision
of fitted model.( Rashid et al.,2009).
The “Lack of Fit F-value”of 0.06 and p-value of
0.998 implies the lack of fit is not significant
relative to the pure error. Insignificant lack of fit
is good as sufficiently good model fitting is
desirable.There is a 99.81% chance that lack of
fit F-value could occurdue to noise.
Table4. Analysis of variance (ANOVA) for the fitted quadractic polynomial catalyzed by alkaline activated
waste bone methyl ester from neem seed oil
Source Coefficient
estimate
Degree of
freedom Sum of square
Mean
squares F-value P-value (Prob>F)
Model 90.38 20 9683.83 484.19 168.19 < 0.0001 significant
A 1.29 1 40.04 40.04 13.91 0.0033
B 1.29 1 40.04 40.04 13.91 0.0033
C 1.29 1 40.04 40.04 13.91 0.0033
D -2.96 1 210.04 210.04 72.96 < 0.0001
E -2.71 1 176.04 176.04 61.15 < 0.0001
AB -1.44 1 33.06 33.06 11.48 0.0060
AC -0.69 1 7.56 7.56 2.63 0.1333
AD -2.69 1 115.56 115.56 40.14 < 0.0001
AE 9.31 1 1387.56 1387.56 482.00 < 0.0001
BC 5.06 1 410.06 410.06 142.44 < 0.0001
BD -3.44 1 189.06 189.06 65.67 < 0.0001
BE 1.81 1 52.56 52.56 18.26 0.0013
CD 3.81 1 232.56 232.56 80.78 < 0.0001
CE -3.19 1 162.56 162.56 56.47 < 0.0001
DE 0.56 1 5.06 5.06 1.76 0.2117
Optimization, Kinetics and Thermodynamics Study of Transesterification of Neem Oil Using Heterogeneous
Catalyst Derived from Waste of Goat Bones
International Journal of Emerging Engineering Research and Technology V7 ● I8 ● 2019 13
𝐀𝟐 -6.62 1 1287.46 1287.46 447.22 < 0.0001
𝐁𝟐 -9.38 1 2578.13 2578.13 895.56 < 0.0001
𝐂𝟐 -7.63 1 1705.46 1705.46 592.42 < 0.0001
𝐃𝟐 -4.25 1 529.83 529.83 184.05 < 0.0001
𝐄𝟐 -9.13 1 2442.46 2442.46 848.43 < 0.0001
Residual 11 31.67 2.88
Lack of fit 6 2.17 0.36 0.061 0.9981 Not significant
Pure error 5 29.50 5.90
Cor Total 31 9715.50
Std Dev. = 1.70, Mean =62.63, C.V% =2.71,Press =91.65, R2=0.9967, Adj R2 =0.9908, Pred R2 =0.9906, Adeq
precision =48.442
Effect of Independent Variables on the Biodiesel
Yield (3D Response Surface Plots)
The interaction effects of variables on biodiesel
production are studied by plotting the three
dimensional response surfaces with the vertical
axis representing biodiesel conversion (response)
and two horizontal axes representing the coded
levels of two independent variables, while keeping
other variables at their central level (0).In figure
2 the three dimensional surface plot shows that
increase inreaction time and catalyst weight
leads to a corresponding increase in yield. The
increment of catalyst weight caused significant
increase in biodiesel yield at low reaction time.
However, the biodiesel yield was slightly
infuenced by the rise of catalyst at higher
reaction time. It was observed that the yield became
steady, when these parameters were increased
further.This might indicate that the transestrification
reaction has reached equilibrium condition, and
further increase may lead to reverse reaction and
thus reduce the biodiesel yield.
The 3D plot shown in figure 3 shows that
increase in catalyst weight and agitation speed
leads to an increase in biodiesel yield. Further
increament of catalyst weight beyond 4wt% and
agitation speed of 400rpm leads to decrease in
biodiesel yield.This may be attributed to the
apperance of emulsion. Figure 4 shows the
response surface plot of reaction time and
methanol to oil ratio on yield. When the other
factors were kept constant, increase in methanol/
oil ratio and reaction time leads to a higher yield. In
other words, increase in time with a corresponding
increase in methanol/oil ratio gives high yield.
Higher production of methyl ester is strongly
favored when high molar ratio is employed for a
certain time of reaction and catalyst weight (Silva et
al.,2010).Figure 5 shows the response surface
plot for the interaction effect between reaction
time and reaction temperature on biodiesel
yield.The surface response indicates that
increment of reaction temperature from low
level to a higher level leads to an increase in
yield of biodiesel under reduced reaction time. It
was also observed that increase of reaction time
does not improve catalytic activity at low reaction
temperature. The reaction processes was in
agreement with Lee’s study in which high
temperature improved the dispersionof catalyst
in the liquid medium with better mass transfer
between the reactant.
Figure2. 3D response surface plots for the interaction
effect of catalyst concentration (A) and reaction
time(D) against yield (%)
Figure3. 3D response surface plots for the interaction effect of catalyst concentration(A) and agitation
speed (E) against yield (%)
Design-Expert® SoftwareFactor Coding: ActualYield (%)
Design points above predicted valueDesign points below predicted value93
24
Yield (%) = 92Std # 30 Run # 19X1 = A: Catalyst conc = 4X2 = D: Reaction time = 4
Actual FactorsB: Methanol/oil ratio = 8C: Temperature = 55E: Agitation speed = 400
3
3.5
4
4.5
5
3
3.5
4
4.5
5
20
40
60
80
100
Yie
ld (
%)
A: Catalyst conc (wt%)D: Reaction time
Design-Expert® SoftwareFactor Coding: ActualYield (%)
Design points above predicted valueDesign points below predicted value93
24
Yield (%) = 92Std # 30 Run # 19X1 = A: Catalyst conc = 4X2 = E: Agitation speed = 400
Actual FactorsB: Methanol/oil ratio = 8C: Temperature = 55D: Reaction time = 4
300
350
400
450
500
3
3.5
4
4.5
5
20
40
60
80
100
Yie
ld (
%)
A: Catalyst conc (wt%)E: Agitation speed (Rpm)
Optimization, Kinetics and Thermodynamics Study of Transesterification of Neem Oil Using Heterogeneous
Catalyst Derived from Waste of Goat Bones
14 International Journal of Emerging Engineering Research and Technology V7 ● I9 ● 2019
Figure4. 3D response surface plots for the interaction
effect of methanol/oil ratio (B) and reaction time(D)
against yield (%)
Figure5. 3D response surface plots for the interaction
effect of reaction temperature (C)and reaction time(D) against yield (%).
Validation of the Optimization result
Optimization study was carried out to obtain the
optimum combination of operating conditions at
which the maximum biodiesel yield is achieved.
In this study, biodiesel yield was set to maximum
value, while the other reaction parameters were
set in a range between high and low levels as
shown. The experimental conditions with the
highest predicted biodiesel yield were selected
for further validation. The result of model
validation is shown in Table 5. The optimum
biodiesel yield of 93% was obtained by
transesterifying neemseed oil with 4wt. % of
catalysts and methanol to oil molar ratio of 8:1
at 550C for 4 h. The predicted biodiesel yield
was 94.3%. This means that the experimental
yield obtained was in good agreement with the
predicted yield, with relatively small percentage
error (1.3 %). This indicated that the proposed
statistical model was suitable for prediction of
optimized biodiesel yield and for optimization
of transesterification process.
Table5. Results of the model validation at optimum conditions catalyzed by alkaline activated waste bone
Catalyst
conc.(wt)
A
Methanol/oil
(mol/mol)
B
Temperature
(oC)
C
Time(Hour)
D
Agitation
speed (rpm)
E
Experimental
Yield (%)
Predicted
yield (%)
(%)
error
4 8 55 4 400 93.0 94.3 1.3
Kinetics of the transesterification Reaction
Transesterification reaction is a consecutive and
reversible reaction being driven by excess
alcohol and a catalyst. The reaction can be
represented as follow (Freedman et al., 1986;
Wenzel et al., 2006; Leevijit et al., 2006; Gemma et
al., 2005 and 2006 and Noureddini and Zhu, 1997):
K1
TG + A ↔ DG + BD (5)
K2
k3
DG + A ↔ MG + BD (6)
k4
k5
MG + A ↔ G + BD (7)
k6
The overall reaction is: TG + 3A 3BD + GL
Where k1, k3 and k5 are rate constants for forward reactions; k2, k4 and k6 are rate constants for
reverse reactions (backward reaction rate). The
lowest value of k is believed to be the rate
determining step of the reaction. Triglyceride is
TG, diglyceride is DG, monoglyceride is MG, glycerol is G and fatty acid methyl ester (biodiesel)
is BD and A is the concentration of alcohol.
The kinetics study of the neem seed oil FAME production using activated waste bone was done
using Langmuir-Hinshelwood-Hougen-Watson
(LHHW) reaction mechanism. The rate and
equilibrium constants were determined by using genetic algorithm (GA) to solve the objective
functions developed with concentration of
various species in the reaction obtained by GC-MS analysis. From the rate and equilibrium
constants obtained at different temperatures, it
could be observed from the rate and equilibrium constants that for all the temperatures considered,
the rate constant for adsorption of triglyceride
was lowest and it increases as temperature
increased. This can be considered as rate determining step (RDS). The rate determining
step is defined as the reaction step with the
highest activation energy.
The net chemical reaction can only proceed at
the rate of the slowest reaction step. It is this
Design-Expert® SoftwareFactor Coding: ActualYield (%)
Design points above predicted valueDesign points below predicted value93
24
Yield (%) = 92Std # 30 Run # 19X1 = B: Methanol/oil ratio = 8X2 = D: Reaction time = 4
Actual FactorsA: Catalyst conc = 4C: Temperature = 55E: Agitation speed = 400
3
3.5
4
4.5
5
6
7
8
9
10
20
40
60
80
100
Yie
ld (
%)
B: Methanol/oil ratio (mol/mol)D: Reaction time
Design-Expert® SoftwareFactor Coding: ActualYield (%)
Design points above predicted valueDesign points below predicted value93
24
Yield (%) = 92Std # 30 Run # 19X1 = C: Temperature = 55X2 = D: Reaction time = 4
Actual FactorsA: Catalyst conc = 4B: Methanol/oil ratio = 8E: Agitation speed = 400
3
3.5
4
4.5
5
45
50
55
60
65
20
40
60
80
100
Yiel
d (%
)
C: Temperature (Oc)D: Reaction time
Optimization, Kinetics and Thermodynamics Study of Transesterification of Neem Oil Using Heterogeneous
Catalyst Derived from Waste of Goat Bones
International Journal of Emerging Engineering Research and Technology V7 ● I8 ● 2019 15
rate determining step that is responsible for the rate equation of an overall reaction. The triglyceride
adsorption reaction has activation energy, 90.98
kJ/mol. The activation (Ea) energy (90.98kJ/mol) of
the rate determining step and the pre-exponential factor, A (1.46×10
10 dm
3 mol
-1min
-1) was calculated
from Arrhenius plots using figure12.
The high value indicates that triglyceride
adsorption was slow and needed high energy
and catalyst to break the energy barrier. The
variation of concentration with time at temperatures
of 450C, 50
0C, and 55
0C are shown in figures 6, 7
and 8, respectively. It could be observed that
concentration decreases as time increases for
triglyceride, diglyceride, monoglyceride and
methanol showing they were consumed to
produce biodiesel and glycerol with biodiesel
been dominant.
Figure6. Variation of reaction time on concentration of TG, DG, MG, ME, FAME and GL at 45oC
Figure7. Effectof reaction time on concentration of TG, DG, MG, ME, FAME and GL at 500C
Figure8. Effect of reaction time on concentration of TG, DG, MG, ME, FAME and GL at 550C
Thermodynamics Properties
The thermodynamic parameters: the standard
free energy (ΔG∘), enthalpy (ΔH∘), and entropy
change (ΔS∘) was estimated to evaluate the
feasibility and endothermic nature of the
transesterification process.
The value of ΔS∘ and ΔH∘ were calculated from
the intercept and slope of the plot of 1n Kfversus
1/T for transesterification catalyzed by acid
activated waste bone.
The calculated values of ΔHo, ΔS
o and ΔG
o are
listed in Table 7. As seen from the results, the
inverse of Kf values increased with increase in temperature and decreases which resulted to a
shift of equilibrium to the left that is production
of methyl ester was favored at high temperatures.
Optimization, Kinetics and Thermodynamics Study of Transesterification of Neem Oil Using Heterogeneous
Catalyst Derived from Waste of Goat Bones
16 International Journal of Emerging Engineering Research and Technology V7 ● I9 ● 2019
The positive values of ΔHo indicated the
endothermic nature of the transesterification.
The transesterification reaction for the endothermic
processes could be due to the increase in
temperature and increase in the rate of diffusion between the three-interphases.
The positive values of ΔSo showed the affinity
of the catalysts for methanol and the increasing
randomness at the solid-solution interface during the transesterification process.
The negative values of ΔGo indicated the feasibility
of the process and the spontaneous nature of the
transesterification reaction. The results showed that the transesterification process was more favorable
at high temperature, due to the endothermic nature
of the transesterification system
Table6. Data for determination of Arrhenius parameters
Temp.(Kelvin) Rate constant (K) TG adsorption InKf 1/T(1/K)
318 1.96E-5 -10.83 0.00314
323 2.17E-5 -10.74 0.00315
328 5.18E-5 -9.87 0.00305
Figure8.Arrhenius plots of the rate determining step
Table7. Transesterification thermodynamic results
Catalyst Temp. (K) ln Kf ∆Go(kJ/mol) ∆H
o(kJ/mol) ∆S
o(kJ/mol)
318 -10.83 -28.63
90.98 0.195 323 -10.74 -28.84
328 -9.87 -26.92
CONCLUSION
Calcium oxide derived from waste goat bone
was used as catalyst for the transesterification of
Neemseed oil in this study. SEM, analysis was
carried out to determine the morphological
structure/microscopic characteristics of the
catalyst. Optimization of transesterification process
of NSO was achieved by five-factorial CCD using
RSM in 32experimental runs. A second-order
model was obtained to predict the NSOB yield as a
function of process variables. Transesterification
of NSO using the CaO derived from waste of
goat bone was optimized using RSM in
combination of central composite design (CCD)
and the optimal conditions were found to be
catalyst weight 4wt%,methanol to oil ratio 8:1,
reaction temperature 550C,reaction time 4hr and
agitation speed 350rpm to achieve a biodiesel
yield of 93.0%. Based on the ANOVA results,
the reaction time and agitation speed was the most
significant factor affecting the transesterification
process. The regression model was found to be
highly significant at 95% confidence level as
correlation coefficients for R-Squared (0.9967),
adjusted R-Squared (0.9908) and predicted R-
Squared (0.9906) was very close to 1 hence an
indication of good correlation and predictive
capabilities. The best fit for experimental data
was the second order kinetic model.
The triglyceride adsorption reaction has
activation energy, 90.98 kJ/mol. The activation
(Ea) energy (90.98kJ/mol) of the rate determining
step and the pre-exponential factor, A (1.46
×1010
dm3 mol
-1min
-1). The high value indicates
that triglyceride adsorption was slow and
needed high energy and catalyst to break the
energy barrier. The positive ∆H, positive ∆S and
the negative ∆G indicate that this process are
endothermic, irreversible, and spontaneous.
Optimization, Kinetics and Thermodynamics Study of Transesterification of Neem Oil Using Heterogeneous
Catalyst Derived from Waste of Goat Bones
International Journal of Emerging Engineering Research and Technology V7 ● I8 ● 2019 17
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Optimization, Kinetics and Thermodynamics Study of Transesterification of Neem Oil Using Heterogeneous
Catalyst Derived from Waste of Goat Bones
18 International Journal of Emerging Engineering Research and Technology V7 ● I9 ● 2019
Citation: Wisdom Chukwuemeke Ulakpa, Callistus Nonso Ude, Ruth. O. Ulakpa, “Optimization, Kinetics and Thermodynamics Study of Transesterification of Neem Oil Using Heterogeneous Catalyst Derived from Waste
of Goat Bones”, International Journal of Emerging Engineering Research and Technology, 7(9), 2019, pp. 7-18
Copyright: © 2019 Wisdom Chukwuemeke Ulakpa. This is an open-access article distributed under the
terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and
reproduction in any medium, provided the original author and source are credited.
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